Aquaporins (AQPs) are membrane water channels expressed in many mammalian tissues that carry out fluid transport. Our lab has generated transgenic knockout mice lacking the four AQPs expressed in eye. Utilizing established and novel methods to study eye physiology in mice, we have obtained evidence for the involvement of AQPs in: ocular surface fluid transport, intraocular pressure regulation, cornea and lens transparency, and retinal signal transduction and fluid balance. Our recent work has also implicated the involvement of AQPs in two novel cellular functions: cell migration and proliferation. Follow-up work in this renewal is focused on mechanism-level analysis of these novel AQP functions, and demonstration of proof- of-concept for new clinical therapies for dry eye syndrome, glaucoma, and retinal neovascularization. Aim 1 will test the involvement of AQP1 in retinal neovascularization. We will determine whether AQP1 deletion/inhibition reduces retinal microvessel proliferation in a mouse model of neonatal hyperoxia followed by normoxia. Biophysical studies will be done to establish the cell-level mechanism of impaired neovascularization in AQP1 deficiency. Aim 2 will establish the cellular mechanism of AQP3-dependent corneal resurfacing following epithelial cell removal. Aim 3 will determine the potential utility of CFTR activators in the therapy of dry eye syndrome. These studies will utilize a mouse model of keratoconjunctivitis sicca, and drug efficacy will be assessed using established outcome measures of ocular surface health, as well as novel biophysical measurements of tear film ionic content, osmolality, and volume. Aim 4 will utilize aquaporin inhibitors, identified by high-throughput screening, as well as AQP1/AQP4 knockout mice, to test whether aquaporin inhibition/knockout can substantially reduce IOP in rodent models of glaucoma, and protect against retinal ganglion cell loss. Together, our studies will establish new roles of aquaporins in the eye with direct implications for new therapies.